Quadriceps function after exercise in patients with anterior cruciate ligament-reconstructed knees wearing knee braces
Davis AG, Pietrosimone BG, Ingersoll CD, Pugh K, and Hart JM. J Athl Train. 2011 46 (6). 615-620.
http://www.ncbi.nlm.nih.gov/pubmed/22488186 (Full text available for free online)
Following anterior cruciate ligament (ACL) reconstruction surgeries many patients wear a variety of knee braces with the intent to increase joint stability and prevent further injury. However, little is known about the neuromuscular effects of these braces during exercise among patients with ACL reconstructions. Therefore, Davis and colleagues completed a crossover study to compare quadriceps muscle activation (maximal contraction and central activation ratio [CAR]) among 14 patients with ACL reconstructions (9 women, 5 men) while they exercised wearing an off-the-shelf ACL functional brace, neoprene sleeve, or nothing on the knee. Patients were included if they had undergone a primary ACL reconstruction at least 2 years prior to all sessions. The patients attended a preliminary session to become familiar with the 20-minute aerobic exercise program (on a treadmill). After that session, the patients attended three sessions and performed the exercise protocol while wearing one of three bracing conditions: a knee brace, neoprene sleeve, or nothing (the order was randomized). The patients performed the quadriceps muscle testing (peak torque during maximal voluntary isometric contraction) 4 times: 1) baseline [before bracing condition or exercise], 2) before exercise but with bracing condition, 3) after exercise with bracing condition, and 4) after exercises with bracing condition removed. To measure the CAR, the patients performed a maximal isometric quadriceps contraction and when the examiner observed a plateau in the torque they triggered an electric stimulation of the quadriceps through electrodes placed on the thigh. This caused an increase in torque by activating the unrecruited portions of the quadriceps muscle. This was performed twice, separated by 30 seconds of rest. CAR is calculated as the maximal torque from the manual contraction divided by the maximal torque generated with the electrical stimulation. The authors found a reduction in maximal voluntary quadriceps contraction force but not CAR when comparing pre-exercise with bracing condition to baseline (braces showed the same pattern as not wearing a brace). The authors also reported a reduction in maximal voluntary quadriceps contraction and CAR during the post-exercise with bracing condition compared to the pre-exercise with bracing condition (once again, braces showed the same pattern as not wearing a brace). Finally, the authors noted that the maximal voluntary quadriceps contraction and CAR were lower during the post-exercise without the bracing condition compared to baseline; during which no one wore a brace. Overall, these findings demonstrated a decrease in quadriceps muscle function and activation following aerobic exercise. However, this finding was not influenced by the application of either a rigid knee brace or neoprene sleeve.
This study provides clinicians with an interesting look at quadriceps muscle recruitment when using various knee braces. While the findings suggest that wearing either a rigid knee brace or neoprene sleeve does not greatly diminish or promote quadriceps recruitment and activation, it is important to keep in mind that none of the data directly addressed knee stability or the perception of knee stability. This is something which would have been interesting to observe; especially since recent research has suggested that a fear of re-injury may be a barrier for some athletes to returning to previous levels of play. Wearing one of the braces may have led some participants to subjectively feel more stable with a brace. If this were true then perhaps bracing ACL-reconstruction patients would be greatly beneficial as it posed no further threat to quadriceps muscle function. If the opposite were true and patients felt no more stable than without a brace then this may lead clinicians to not recommend either type of brace as it would not benefit the patient. Tell us what you think. Do you recommend a brace following ACL reconstruction? What type of brace do you typically recommend?
Written by: Kyle Harris
Reviewed by: Jeffrey Driban
Related Posts:Davis AG, Pietrosimone BG, Ingersoll CD, Pugh K, & Hart JM (2011). Quadriceps function after exercise in patients with anterior cruciate ligament-reconstructed knees wearing knee braces. Journal of Athletic Training, 46 (6), 615-20 PMID: 22488186